toolchain/51750: gdb is useless on some core files

[martin%NetBSD.org@localhost]

>Number:         51750
>Category:       toolchain
>Synopsis:       gdb is useless on some core files
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 28 16:05:00 +0000 2016
>Originator:     Martin Husemann
>Release:        NetBSD 7.99.53
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD night-owl.duskware.de 7.99.53 NetBSD 7.99.53 (NIGHT-OWL) #450: Wed Dec 28 12:18:50 CET 2016 martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/amd64/compile/NIGHT-OWL amd64
Architecture: x86_64
Machine: amd64
>Description:

On some core files, like the ones generated by the Xorg server in PR lib/51749,
gdb does not properly map core memory and can not produce ussable backtraces.
It also seems to be missing all symbols, e.g. "list main" does not work.

I have uploaded that core, debug-info and binary to:
	https://www.NetBSD.org/~martin/bad_core.tgz

>How-To-Repeat:
s/a

>Fix:
n/a